impl sqrt and b search

scala/src/main/scala/ch15_bsearch/BSearch.scala

@@ -1,20 +1,50 @@
 package ch15_bsearch
 
-object BSearch {
-    def search(nums: Array[Int], target: Int): Int = {
-        var low = 0
-        var high = nums.length - 1
-        while(low <= high){
-            val mid = low + ((high - low) >> 2)
-            if(nums(mid) > target){
-                high = mid - 1
-            } else if (nums(mid) < target){
-                low = mid + 1
-            } else {
-                return mid
-            }
-        }
+import scala.math.abs
 
-        return -1
+object BSearch {
+
+  def search(items: Array[Int], target: Int): Int = {
+    var low = 0
+    var high = items.length - 1
+    while (low <= high) {
+      val mid = low + (high - low) / 2
+      if (items(mid) == target) {
+        return mid
+      } else if (items(mid) > target) {
+        high = mid - 1
+      } else {
+        low = mid + 1
+      }
     }
+
+    -1
+  }
+
+  def sqrt(x: Double, precision: Double): Double = {
+
+    require(precision > 0, "precision must > 0")
+    require(x > 0, "input value for sqrt must > 0")
+    var low = 0.0
+    var high = x
+    val actualPrecision = precision / 10
+
+    if (x > 0 && x < 1) {
+      low = x
+      high = 1
+    }
+    while (high - low > actualPrecision) {
+      val mid = low + (high - low) / 2
+      if (abs(mid * mid - x) < actualPrecision) {
+        //find it
+        return mid
+      } else if (mid * mid > x) {
+        high = mid
+      } else {
+        low = mid
+      }
+    }
+    throw new IllegalStateException("could not determine the sqrt value for " + x)
+
+  }
 }

scala/src/main/scala/ch15_bsearch/BSearchRecursive.scala

@@ -1,22 +1,23 @@
 package ch15_bsearch
 
 object BSearchRecursive {
-    def search(nums: Array[Int], target: Int): Int = {
-        return searchInternal(nums, target, 0, nums.length - 1)
+
+  def search(items: Array[Int], target: Int): Int = {
+    _search(items, target, 0, items.length - 1)
+  }
+
+  private[this] def _search(items: Array[Int], target: Int, low: Int, high: Int): Int = {
+    if (low > high) {
+      return -1
     }
 
-    def searchInternal(nums:Array[Int], target: Int, low: Int, high: Int): Int = {
-        if(low <= high){
-            val mid = low + ((high - low) >> 2)
-            if(nums(mid) > target){
-                searchInternal(nums, target, low, mid - 1)
-            } else if (nums(mid) < target){
-                searchInternal(nums, target, mid + 1, high)
-            } else {
-                return mid
-            }
-        }else{
-            return -1
-        }
+    val mid = low + (high - low) / 2
+    if (items(mid) == target) {
+      mid
+    } else if (items(mid) > target) {
+      _search(items, target, low, mid - 1)
+    } else {
+      _search(items, target, mid + 1, high)
     }
+  }
 }

scala/src/test/scala/ch15_bsearch/BSearchRecursiveTest.scala

@@ -0,0 +1,25 @@
+package ch15_bsearch
+
+import ch12_sorts.QuickSort
+import org.scalatest.{FlatSpec, Matchers}
+
+import scala.util.Random
+
+class BSearchRecursiveTest extends FlatSpec with Matchers {
+
+  behavior of "BSearchRecursiveTest"
+
+  it should "search with exist value" in {
+    val length = 50000
+    val array = new Array[Int](length)
+    val rnd = new Random()
+    for (i <- Range(0, length)) {
+      array(i) = rnd.nextInt()
+    }
+
+    val target = array(2698)
+
+    BSearchRecursive.search(QuickSort.quickSort(array), target) should be > -1
+  }
+
+}

scala/src/test/scala/ch15_bsearch/BSearchTest.scala

@@ -0,0 +1,37 @@
+package ch15_bsearch
+
+import ch12_sorts.QuickSort
+import org.scalatest.{FlatSpec, Matchers}
+
+import scala.util.Random
+
+class BSearchTest extends FlatSpec with Matchers {
+
+  behavior of "BSearchTest"
+
+  it should "search with exist value" in {
+    val length = 50000
+    val array = new Array[Int](length)
+    val rnd = new Random()
+    for (i <- Range(0, length)) {
+      array(i) = rnd.nextInt()
+    }
+
+    val target = array(2698)
+
+    BSearch.search(QuickSort.quickSort(array), target) should be > -1
+  }
+
+  it should "calculate sqrt value -1 " in {
+    val x = 4
+    val precision = 0.000001
+    BSearch.sqrt(x, precision) should equal(2.0)
+  }
+
+  it should "calculate sqrt value -2 " in {
+    val x = 0.04
+    val precision = 0.000001
+    BSearch.sqrt(x, precision) should equal(0.2 +- precision)
+  }
+
+}